In a conventional impeller washing machine, water levels of inner tub and outer tub are the same during the washing, such that the inner tub and the outer tub need to be filled with washing water, thus a relatively large amount of washing water is required. However, the water between the inner tub and the outer tub does not involve in the washing, and only the water in the inner tub actually involves in the washing, such that water resources are wasted. Furthermore, the excessive water between the inner tub and the outer tub will also reduce a concentration of detergent, such that a larger amount of detergent needs to be put in to achieve a good washing effect, which undoubtedly also causes a waste of the detergent.
In order to further improve water saving performance, a washing machine with a holeless inner tub exists in the related art, in which the inner tub is configured as a holeless stainless steel tub, such that a water level difference is formed between the inner tub and the outer tub, and the washing water can be saved. Meanwhile, this washing machine is provided with a water outlet passage above the inner tub, and the washing water flows upwardly along a wall of the inner tub and is discharged via the water outlet passage under the action of a centrifugal force during dehydration, thereby achieving a purpose of discharging the water.
However, when this washing machine is discharging the water, a relatively large centrifugal force needs to be produced by an electric motor to realize the water discharge. Therefore, this washing machine needs to employ a high-power electric motor, which is adverse to saving electric power and controlling noise and vibration.